A vehicle air bag module typically includes an air bag and an inflator disposed within a container. The container comprises a reaction device (e.g., a reaction can or a reaction plate) and a cover coupled to the reaction device to complete an enclosure for the inflator and the air bag. The module is assembled by coupling the air bag and inflator to the reaction device by means of fasteners such as bolts or rivets, and then coupling the cover to the reaction device by means of additional fasteners. The module is installed in a vehicle by coupling the reaction device to a structural part of a vehicle (e.g., a steering column) by means of still more fasteners.
At the onset of a vehicle collision, the inflator rapidly generates an inert, non-toxic gas, and directs that gas into the air bag. The gas forces the air bag through the cover and inflates the air bag. During inflation of the air bag, the inflator and the air bag apply significant forces to the reaction device. Those forces are, in turn, taken up and transmitted to the vehicle by (i) the reaction device, (ii) the fasteners which couple the inflator and the air bag to the reaction device and (iii) the fasteners which couple the reaction device to the vehicle.
Using fasteners such as bolts or rivets in assembling an air bag module does present some important procedural and economic considerations, especially with respect to the mass production of air bag modules. One procedural consideration is that in assembling an air bag module, bolt holes formed in an air bag and in an inflator housing must be carefully aligned with bolt holes in the reaction device in order to couple the air bag and the inflator properly with the reaction device. Another procedural consideration is that the bolts or rivets which couple an air bag and/or an inflator to a module housing are normally attached to each of those components sequentially rather than simultaneously. An important economic (or procurement) consideration is that the bolts and rivets used in the assembly and installation of the module are additional parts which generally have to be sourced separately from the other components of the module.